Re: [BUG] ideapad_laptop: fans do not ramp up properly under CPU load on Lenovo IdeaPad 3 15ALC6 Ub (82KU)

[Sourajyoti Basak]

On 02/06/26 8:43 pm, Sourajyoti Basak wrote:
> On 09/05/26 9:00 pm, Sourajyoti Basak wrote:
>> Hello,
>>
>> I am using a Lenovo IdeaPad 3 15ALC6 Ub (82KU), and I am encountering an
>> issue where the laptop fans do not respond appropriately to increasing
>> CPU temperatures under Linux.
>>
>> System information:
>> Laptop: Lenovo IdeaPad 3 15ALC6 Ub
>> BIOS version:GLCN46WW
>> System performance mode in BIOS: Extreme Performance
>> Kernel: Linux 7.0.5-1-cachyos
>> Distribution: CachyOS
>> CPU: AMD Ryzen 5 5500U (12) @ 4.06 GHz
>>
>> Issue description:
>> Under sustained CPU load (for example using stress -c $(nproc)), CPU
>> temperatures rapidly increase to around 95-100°C. However, the fans do
>> not ramp to maximum speed as expected. Therefore, the system begins
>> thermal throttling after some time in this state.
>>
>> As a result:
>>
>> - The CPU reaches thermal throttling temperatures.
>> - CPU frequencies drop significantly once throttling begins.
>> - Fan RPM appears capped or insufficient despite high temperatures.
>> - The issue appears consistently reproducible on my laptop and another
>>   person's laptop.
>>
>> Additional observations:
>>
>> - The issue persists across multiple recent kernel versions.
>> - No hardware issues appear to be present. (Verified that the fans can
>> indeed
>>   ramp up to max speed by 
>> `echo 1 | sudo tee /sys/bus/platform/drivers/ideapad_acpi/VPC2004:00/
>> fan_mode`,
>> which makes the fan enter "dust cleaning mode," causing it to ramp up to
>> max speed
>> and then back down to 0 RPM about 10 times.)
>>
>> Attachments:
>> - DSDT in `DSDT.gz`
>> - `dmidecode` in `dmidecode.txt`
>>
>> Data Collected during `stress -c $(nproc)` until thermal throttling:
>> - EC information collected in a CSV file named `ec.csv`
>>   (using `sudo ec_probe monitor -i 0.5 -r ec.csv` from the NBFC project)
>> - `sensors` information in `sensors.log`
>> - CPU frequencies in `cpu-freq.log`
>> - `dmesg` in `dmesg-live.log`
>>
>> Thank you for your time.
>>
>> Best regards,
>> Sourajyoti Basak
> 
> 
> Hello everyone,
> 
> Just a gentle ping on this bug report. The thermal throttling issue is
> still present. Please let me know if there is any further ACPI/EC
> debugging information I can provide.
> 
> Best Regards,
> Sourajyoti Basak

Hello everyone,

Just wanted to confirm that this issue still exists after updating to
the latest BIOS version (`GLCN68WW`) and on the latest linux kernel
version `Linux 7.1.2-3-cachyos`.

Best Regards,
Sourajyoti Basak